Hearing aid



FIG. 1 is a side view of a hearing aid of our design;

FIG. 2 is another side view of the hearing aid of our design;

FIG. 3 is a perspective view of the hearing aid of our design;

FIG. 4 is another perspective view of the hearing aid of our design;

FIG. 5 is another perspective view of the hearing aid of our design;

FIG. 6 is another perspective view of the hearing aid of our design; and,

FIG. 7 is another perspective view of the hearing aid of our design.

The broken lines in the drawing views are included for the purpose of illustrating portions of the hearing aid that form no part of the claimed design. 

The ornamental design for a hearing aid, as shown and described. 